PHCL2610 Lecture 2: Nervous System
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Questions and Answers

What role do action potentials play in neuronal communication?

  • They only affect the neuron's shape.
  • They are the primary means of transmitting information. (correct)
  • They prevent the release of neurotransmitters.
  • They help neurons grow.

    • How do neurons primarily communicate with each other?

  • By changing their shape.
  • Only by mechanical means.
  • Using electrical signals and neurotransmitters. (correct)
  • Through the release of hormones.

    • What is necessary to create an action potential in neurons?

  • Stable resting membrane potential.
  • A significant change in membrane potential. (correct)
  • Excess neurotransmitter release.
  • A constant voltage supply.

    • Which of the following statements about resting membrane potential is correct?

    <p>It is crucial for generating action potentials. (A)</p> Signup and view all the answers

    What happens when an action potential travels down the axon?

    <p>It activates cell communication further along the neuron. (C)</p> Signup and view all the answers

    Which of the following best describes the propagation of an action potential?

    <p>It occurs through a sequence of depolarization and repolarization. (B)</p> Signup and view all the answers

    What occurs at the synapse between two neurons?

    <p>Neurotransmitters are released for communication. (D)</p> Signup and view all the answers

    What is a primary function of neurotransmitters in neuronal communication?

    <p>To facilitate cell-cell interaction. (B)</p> Signup and view all the answers

    Which of the following is NOT a reason electrical signals are important in neurons?

    <p>They prevent action potentials from occurring. (B)</p> Signup and view all the answers

    Which ion primarily determines the resting membrane potential in neurons?

    <p>K+ (C)</p> Signup and view all the answers

    What is the resting membrane potential (RMP) of skeletal muscle cells?

    <p>-90 mv (A)</p> Signup and view all the answers

    What equation is used to predict the equilibrium potential for ions?

    <p>Nernst Equation (B)</p> Signup and view all the answers

    How does the Na+ pump contribute to maintaining the resting membrane potential?

    <p>By transporting 3 Na+ out and 2 K+ into the cell (C)</p> Signup and view all the answers

    What factors are essential for the production and maintenance of the resting membrane potential?

    <p>Concentration differences and membrane permeability (B)</p> Signup and view all the answers

    Which statement best describes the membrane potential at any time?

    <p>It is closest to the equilibrium potential of the most permeable ion. (A)</p> Signup and view all the answers

    What is the primary reason K+ contributes significantly to the resting membrane potential?

    <p>K+ is highly permeable and leaks out of the cell. (C)</p> Signup and view all the answers

    What is the role of Na+ channels in the resting membrane potential?

    <p>They have low permeability, resulting in minimal Na+ leakage. (D)</p> Signup and view all the answers

    In which type of cell is the resting membrane potential estimated to be between -7 mv to -14 mv?

    <p>Red blood cells (D)</p> Signup and view all the answers

    What primarily determines the resting membrane potential (RMP) of neurons?

    <p>Ion concentration differences across the membrane (A)</p> Signup and view all the answers

    Which type of ion channels randomly open and close without a stimulus?

    <p>Leak or passive channels (C)</p> Signup and view all the answers

    What initiates the activation of ligand-gated channels?

    <p>The binding of a ligand or molecule (A)</p> Signup and view all the answers

    Which statement about gated ion channels is true?

    <p>They open only in response to specific stimuli. (A)</p> Signup and view all the answers

    Which ion is most relevant for leak channels in neurons?

    <p>Potassium (K+) (C)</p> Signup and view all the answers

    Where are voltage-gated channels primarily located in neurons?

    <p>Along the axon and Node of Ranvier (D)</p> Signup and view all the answers

    What best describes the action potential (AP)?

    <p>A brief reversal of the membrane potential (B)</p> Signup and view all the answers

    Which mechanical stimuli activate mechanically-gated channels?

    <p>Vibration and touch (C)</p> Signup and view all the answers

    What is the typical range for the resting membrane potential (RMP) in neurons?

    <p>-40 to -90 mV (C)</p> Signup and view all the answers

    What ions are primarily responsible for the RMP difference across the neuronal membrane?

    <p>Potassium (K+) and sodium (Na+) (A)</p> Signup and view all the answers

    Flashcards

    Electrical Signals

    Signals used by neurons to transmit information to other cells.

    Neuronal Communication

    Process by which neurons exchange signals via electrical activity or neurotransmitters.

    Action Potentials

    Rapid electrical impulses that travel along axons to facilitate communication.

    Neurotransmitters

    Chemicals released by neurons to communicate between cells.

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    Axon

    Part of a neuron that conducts electrical impulses away from the cell body.

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    Resting Membrane Potential

    The stable, negative charge inside a neuron at rest.

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    Propagation of Action Potential

    The process by which an action potential travels along the axon.

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    Cell-cell Communication

    Interaction between cells through signaling mechanisms.

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    Electrical Activity

    The changes in electrical charge that occur in neurons during signaling.

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    Information Transmission

    The method by which neurons convey signals and data.

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    Ion Channels

    Proteins in the membrane that allow the selective movement of ions in and out of neurons.

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    Leak Channels

    Channels that randomly open and close, allowing high permeability to ions.

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    Gated Channels

    Ion channels that open or close in response to specific stimuli.

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    Ligand-Gated Channels

    Channels activated by the binding of a molecule (like neurotransmitters) to increase ion permeability.

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    Mechanically-Gated Channels

    Channels activated by mechanical stress, like pressure or vibration.

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    Voltage-Gated Channels

    Channels that open in response to changes in membrane potential, crucial for action potentials.

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    Ion Concentrations

    The balance of ions (like K+ and Na+) inside versus outside the neuron that affects membrane potential.

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    Neuronal Activation

    The process initiated by stimulus leading to action potentials in neurons.

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    Equilibrium Potential

    The membrane potential where ion concentration is balanced across the membrane.

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    Nernst Equation

    A mathematical formula used to calculate the equilibrium potential for specific ions.

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    Goldman Field Equation

    Describes the membrane potential considering ion concentrations and permeability.

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    Resting Membrane Potential (RMP)

    The baseline electric charge inside a cell at rest, typically negative.

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    Membrane Permeability

    How easily ions can pass through the cell membrane.

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    Sodium-Potassium Pump

    A transport mechanism that maintains RMP by moving Na+ out and K+ in.

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    K+ Permeability

    The ease with which potassium ions can cross the neuron membrane.

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    Threshold Potential

    The membrane potential that must be reached for an action potential to occur.

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    Study Notes

    Lecture 2 PHCL2610: Nervous System

    • Lecturer: Ana Maria Oyarce Ph.D.
    • Department: Pharmacology - HEB280C
    • Office hours: TBD or by appointment
    • Phone: (419)383-1919
    • Email: [email protected]

    Topics

    • Electrical Signals

    • Channels

    • Resting Membrane Potential

    • Material: Vander's Human Physiology 16th Edition, Copyright 2023, Chapter 6, Section B: Membrane Potentials

    Neuronal Communication

    • Neurons communicate using specific signals.
    • Cell-cell communication happens through electrical activity or neurotransmitter release.

    Why Electrical Signals in Neurons are Important?

    • Electrical signals (action potentials/nervous impulses) transmit information between neurons and other cells.
    • Action potentials are crucial for cell-cell communication.
    • Action potentials travel along the axon, triggering electrical activity or neurotransmitter release in the next cell.

    Electrical Signals in Neurons

    • Neurons at rest exhibit a resting membrane potential (RMP).
    • Activated neurons produce action potentials (APs).
    • RMP and AP production depend on ion concentration differences inside and outside the neuron.
    • The lipid bilayer of the plasma membrane acts as an insulator, and ion movement occurs through ion channels embedded in the membrane.
    • Ion channels open or close in response to specific stimuli.

    Types of Ion Channels

    • Ion channels are present in the plasma membrane.
    • Classified based on activation mechanism:
      • Leak/passive (non-gated) channels: randomly open and close.
      • Gated channels: open or close in response to a stimulus.

    Leak or Passive Channels

    • Permeability to ions is high.
    • Channels alternate between open and closed positions.
    • Leak channels in neurons are primarily K+, Na+, and Cl-.
    • K+ is most relevant.
    • Present in all cells, including dendrites, cell bodies, and axons of neurons.

    Gated-Ion Channels

    • Three main types based on activation:
      • Ligand-gated channels
      • Mechanically gated channels
      • Voltage-gated channels

    Ligand-Gated Channel

    • Binding of a ligand (e.g., neurotransmitter, hormone, ion) to a ligand-gated channel changes its permeability to an ion.
    • Primarily located in dendrites and cell bodies, concentrating at the synapse.

    Mechanically-Gated Channels

    • Mechanical stimuli (e.g., vibration, touch, pressure) induce conformational changes in the receptor, activating the channel.
    • Found in receptors of auditory, internal organs, and skin.

    Voltage-Gated Channels

    • Activate in response to changes in membrane potential.
    • Exhibit ion selectivity.
    • Crucial for action potential generation and propagation.
    • Found along unmyelinated axons, nodes of Ranvier (myelinated axons), and the axon hillock.

    Membrane Potentials

    • Resting membrane potential (RMP): Voltage difference across the membrane when the cell isn't stimulated.
    • Action potential (AP): Brief reversal in membrane potential following neuron activation.

    Resting Membrane Potential

    • RMP is due to differences in ion concentrations across the membrane.
    • RMP in neurons is typically between -40 and -90 mV (typically -70 mV).
    • Negative charges are inside the neuron, and positive charges are outside.
    • Distribution of K+ and Na+ ions is key. (Inside Neuron: High K+, Outside Neuron: High Na+.)

    Why an Electrical Potential is Generated?

    • Equal K+ concentration on both sides, no net flux of K+ indicates closed channels.
    • K+ movement generates a charge difference.
    • Electrical potential opposes further K+ movement.
    • Electrical potential matches concentration gradient. This is known as the electrochemical equilibrium.
    • Same principle applies to other ions.

    Nernst Equation

    • Predicts the equilibrium potential for an ion.
    • Includes ion concentration inside and outside cells, charge, universal gas constant, temperature, and Faraday's constant.

    Several Ions Contribute to The Membrane Potential

    • Membrane potential depends on K+, Cl-, and Na+.
    • The Goldman Field Equation describes the membrane potential, considering ion concentrations and membrane permeabilities to each ion.
    • The neuron's membrane potential is most influenced by the ion with the highest permeability. (Most permeable ion is K+ for neurons.)

    Resting Membrane Potential (cont.)

    • The magnitude of the resting potential depends on:
      • Differences in specific ion concentrations.
      • Differences in membrane permeability to ions. (Number of channels open.)
    • All cells have a resting membrane potential. (e.g., skeletal muscle = -90 mV, neurons = -70 mV, red blood cell = -7 to -14 mV.)

    How is the RMP Produced and Maintained?

    • Leak channels for K+ and Na+ are open at rest.
    • K+ diffuses out of the neuron (high permeability).
    • Na+ slightly leaks into the neuron.
    • The sodium-potassium pump maintains RMP by actively transporting Na+ out and K+ into the neuron. (Maintains RMP equilibrium by using ATP.)

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    Explore the fundamentals of the nervous system in Lecture 2 of PHCL2610. This quiz covers essential topics such as electrical signals, resting membrane potential, and neuronal communication. Gain a deeper understanding of how neurons transmit crucial information through action potentials.

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